This invention relates to a novel process of preparing nitrogen trifluoride by reaction between fluorine gas and an ammonium complex of a metal fluoride.
Nitrogen trifluoride NF.sub.3 is a colorless gas under normal conditions and has a boiling point of about -129.degree. C. and a melting point of about -208.degree. C. This compound is useful as a fluorine source material in the preparation of fluoroolefins and also as an oxidizer for a high-energy fuel.
Nitrogen trifluoride is prepared usually by direct fluorination of ammonia in vapor phase or by electrolysis of ammonium hydrogenfluoride. Vapor phase reaction between hydrogen azide and oxygen difluoride is also known. U.S. Pat. No. 3,304,248 proposes to carry out reaction between nitrogen and fluorine by forcing nitrogen gas heated to a temperature above 100.degree. C. to pass through a plasma arc and simultaneously introducing fluorine gas into a post-arc region very close to the anode. The reactions in these methods are vapor phase reactions which are relatively violent and not easy to control. Furthermore, in the popular methods it is necessary to take troublesome measures for the prevention of formation of a flammable or explosive gas atmosphere containing hydrogen.
Japanese Patent Application Publication No. 55-8926(1980) proposes to prepare nitrogen trifluoride by reaction between ammonium hydrogenfluoride in molten state with fluorine gas. However, this method does not seem industrially favorable firstly because the gas-liquid reaction in this method is not so easy to control and causes significant corrosion of the apparatus and also because the yield of nitrogen trifloride is relatively low.